New method for determining the permeability tensor of magnetized ferrites in a wide frequency range

To provide a broad-band method for measuring the complex permeability tenso r components of magnetized ferrites we have realized a nonreciprocal rectan gular waveguide cell. A network analyzer setup is used to measure the scatt ering parameters of the cell over a wide range of frequencies. The nonrecip rocity of the cell permits the determination of the permeability tensor com ponents in a single experimental phase. Complex permittivity and complex co mponents of the permeability tensor are computed from a data-processing pro gram, taking into account higher order modes excited at the cell discontinu ities and using a numerical optimization procedure to match calculated and measured values of the S-parameters. We have studied the convergence of the calculated S-parameters as the number of modes taken into account in the c alculations. Sensitivity to the input parameters for the optimization algor ithm is discussed. A thru-reflect-line calibration in conjunction with a sp ecific sample holder is used to eliminate systematic errors inherent in the S-parameter measurements. Measured complex permeability tensor components data for microwave ferrites are presented at X-band frequencies (8-12 GHz), Experimental results are in good agreement with theoretical results given by the ferromagnetic material theory.